This invention relates to a directional boring machine with a steerable, fluid assisted mechanical boring head for drilling substantially horizontal boreholes under a roadway or other obstruction.
Using boring machines with a steerable bit or head for drilling horizontal boreholes under a roadway or other obstruction is a well known practice. The process of providing such boreholes is generally referred to as xe2x80x9ctrenchlessxe2x80x9d digging, since an open trench is not required. A key to the operation of such a boring device is to have an effective steerable boring bit or head. If the bit is steerable, the operator can redirect the borehole along the proper path if it begins diverting from the desired path, and also allows the operator to steer around obstructions underground.
Many boring heads have been designed which have such a steering feature. However, there is a continuing need to develop boring heads which have better directional control, operate in a variety of soil conditions effectively and provide enhanced cutting action.
The present invention is directed to a directional boring machine comprising a frame, a rotary machine supported on the frame, a drill string operatively connected to the rotary machine to drive the rotation of the drill string; and a directional multi-blade boring head attached to the end of the drill string. The boring head comprises a body having a central axis of rotation and a blade assembly mounted on the body.
In one embodiment the blade assembly has a first blade defining a deflecting surface at an oblique angle to the central axis of rotation of the body and a second blade defining a deflecting surface at an oblique angle to the central axis of rotation of the body. The first and second blades extend at an angle relative to each other. At least one additional blade extends from the blade assembly between the deflecting surface. The deflecting surfaces of a first and second blade deflect the boring head as the boring machine advances the drill string without rotation, and the directional multi-blade boring head drills a relatively straight borehole as the boring machine advances the drill string with rotation.
In another embodiment, the blade assembly has a base and a blade extending from the base. The base is attached to the lower surface of the body of the boring head, and the base defines a first plane. The blade terminates in a forward end, and the blade defines a second plane intersecting the first plane of the base, so that the blade angles upward relative to the base. The blade has a thickness tapering gradually towards the forward end, and the forward end defines a plurality of teeth. Each tooth has a contact side and a back side, the contact side being the side that impacts the earth first as the boring head is rotated on the drill string, and the back side being the side opposite the contact side. The back side of each tooth is cut away forming a recess between the back side of the tooth and the surface being bored. Still further, the plurality of teeth includes a first set on a first side of the blade and a second set of teeth on the second side of the blade. The first set is substantially similar in size and configuration to the second set of teeth, but extends slightly forward of the second set of teeth.